Optical system for superimposing images

ABSTRACT

An optical system for superimposing images on a single image plane from both directional and non-directional sources is disclosed. An apertured mirror is placed at an angle to a source of a diffused light image, to reflect light therefrom toward an image plane, such as a display screen or photosensitive sheet. A second, directional image is projected by an optical system through the aperture toward the image plane. A single objective lens assembly placed between the mirror and the image plane acts on light rays from both sources producing both images in superimposition in the image plane.

United States Patent [151 3,673,933 ilamann July 4, 1972 541 OPTICALSYSTEM FOR 3,495,267 2 1970 Brodie ..95/l.l x

SUPERIMPOSING IMAGES ()mer F. Hamann, La Jolla, Calif.

Stromberg Datagraphix, Inc., San Diego, Calif.

Inventor:

Assignee:

Filed: Aug. 3, 1970 Appl. No.: 60,322

U.S.Cl ..95/l.1,95/l2, 353/37, 353/81, 355/43, 355/65, 355/66 Int. Cl...G03b 15/10 FieldofSearch ..95/1.1, 12;355/40, 43,51, 355/65, 66;353/37, 81

References Cited UNITED STATES PATENTS 10/1969 Greenly et a1 ..355/40 XL/\ M P CONTROL Primary Examiner-Samuel S. Matthews AssistantExaminer-Richard A. Wintercom Atiorney-John R. Duncan [57] ABSTRACT Anoptical system for superimposing images on a single image plane fromboth directional and non-directional sources is disclosed. An aperturedmirror is placed at an angle to a source of a diffused light image, toreflect light therefrom toward an image plane, such as a display screenor photosensitive sheet. A second, directional image is projected by anoptical system through the aperture toward the image plane. A single0bjective lens assembly placed between the mirror and the image planeacts on light rays from both sources producing both images insuperimposition in the image plane.

8 Claims, 2 Drawing Figures FILM 3 DRIVE CONTROL 32 SYSTEM TUBE CONTROLCONTROL PATENTEDJUL 41912 SHEET 201 2 m OI IN VENTOR.

OMER F. HAMANN ATTORNEY BACKGROUND OF THE INVENTION It is oftendesirable to superimpose light images from plural sources on a singleimage plane in many display and photographic applications. For example,in computer output microfilming applications the capability ofsimultaneously recording data from a cathode ray tube screen and abusiness form onto microfilm in superimposition is often useful. Also,in large. screen display systems, it may be desirable to project a mapbackground, a grid pattern overlay and data or radar images from acathode ray tube on a display screen in superimposition.

Conventional image combining systems either project images alongdifferent, closely-spaced, axes or use a beamsplitter to permitprojection of plural images along one axis.

However, where separate projection axes are used, image aberrations,such as keystoning and poor image superimposition occur. Beam-splittersuse partially-reflecting or dichroic mirrors in the optical path betweenthe plural light sources and the image plane. The beam-splitter isplaced at an angle to the image plane. The image sources are arranged sothat light forming one image passes through the beam-splitter to theimage plane while the light forming the other image is reflected to theimage plane. However, since the light from each source is partiallytransmitted and partially reflected, and partially absorbed in metallicmirrors, less than half of the available light reaches the image plane.

Dichroic beam-splitters are more effective where the sources emit lightof different wavelengths and the light rays from each source strike thebeam-splitter at a particular angle. Dichroic mirrors can be designed totransmit one wavelength range and reflect the other. However, they areless useful where both image sources emit in the same wavelength ranges.Where one or both images are in multiple colors, dichroic beam-splitterswill distort the color rendition of the system.

Beam-splitters are fragile and susceptible to damage caused byvibration, cleaning and improper mounting. When thick beam-splitters areused aberrations are introduced since skew, saggital and tangentalcomponents of light emission have different optical path lengths.Beam-splitters are difficult to construct to the desired degree offlatness without increasing the thickness to the point where suchaberrations become virtually impossible to correct.

Thus, there is a continuing need for improved optical systems forsuperimposing images from a plurality of sources in register on asimpleimage plane.

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto provide an optical system for superimposing images which overcomesthe above-noted problems.

Another object of this invention is to provide an optical system forsuperimposing images which utilizes more of the available light withoutintroducing optical aberrations.

Still another object of this invention is to provide an imagesuperimposing optical system of improved simplicity and reliabilit Tiieabove objects, and others, are accomplished in accordance with thisinvention by an optical image superimposing system utilizing a reflectorwith an on-axis aperture to permit plural images to be directed along asingle optical axis to a single image plane.

This system permits light rays from two or more image sources to have acommon optical axis and a common image plane, which may typically be adisplay screen or a photosensitive surface. A directional image, such asone from a conventional transparency projector, may be combined with oneor more non-directional images from diffuse sources such as cathode raytube screens. This system eliminates optical problems caused by multipleoff-axis projectors without introducing the many problems inherent inthe use of beamsplitters or dichroic mirrors.

BRIEF DESCRIPTION OF THE DRAWING Details of the invention, and apreferred embodiment thereof, will be further understood upon referenceto the drawing, wherein:

FIG. 1 shows a schematic representation of an optical system forsuperimposing images; and

FIG. 2 shows a schematic representation of an alternative embodiment forsuperimposing images.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, there isseen a schematic representation of a computer output microfilming systemusing the optical system of this invention. In such a microfilmingsystem, it is desired to produce superimposed latent images in microfilm10 from both data displayed on the screen of cathode ray tube 12 andbusiness form slide 24.

Mirror 14 is arranged to reflect light from tube 12 through objectivelens system 16 to microfilm 10. An aperture 18 in mirror 14 permitslight from light source 20 to also reach microfilm l0. Aperture 18preferably has an elliptical shape, so that it will appear circular whenviewed along the optical axis through the aperture. Source 20 isapproximately a point source, which is imaged by lens 22 in a verticalplane passing through the center of aperture 18. Thus, light passingfrom source 20 through form slide 24 substantially entirely passesthrough aperture 18 to lens 16 which projects an-image of the slide onthe microfilm.

Aperture 18 may be relatively small without appreciably decreasing thebrightness of the form slide image. Since the area of aperture 12 isrelatively small compared to the area of mirror 14, relatively little ofthe light reaching mirror 14 from tube 12 is lost through the aperture.The preferred size of aperture 18 will depend upon the size of lightsource 20, the magnification between the vertical planes through lightsource 20 and through aperture 18 and the spatial frequencies in formslide 24. Generally, an aperture size just sufficient to pass thesignificant portion of the zero order diffraction pattern of form slide24 is preferred.

Mirror 14 may comprise any suitable material. A highly reflective metalmirror is preferred, since such a mirror is strong and may bemanufactured to a high degree of flatness. Such a mirror can be cleanedwith little fear of damage.

Lens 16 and 22 may comprise any suitable lens systems, and any suitablecathode ray tube, such as a shaped beam tube, may be used as tube 12.

In operation, the entire system is operated and controlled by aconventional system logic and control means 30. Typically, control means30 may receive information from a computer tape reader and, through tubecontrol 32, cause an image of the information to appear on the face oftube 12. The system logic and control circuits activate lamp control 34to flash an image of slide 20 onto microfilm 10 when required. Aftereach microfilm frame is exposed, system control 30 causes film drivecontrol 36 to activate film drive motor 38 to advance one frame of filmfrom supply reel 40 toward take-up reel 42. These operations arecontinued at high speed to sequentially record information on themicrofilm.

Of course, this optical system is capable of projecting many differenttypes of information on other surfaces. For example, forms slide 20might project a map image onto a projection screen in place of microfilm10, and tube 12 might provide both radar and data images insuperimposition.

An alternative embodiment in which two diffuse images are combined witha directional image is shown in FIG. 2. In this embodiment, the imagesare presented on a display screen 50, which may be a front or rearprojection screen.

A pair of apertured reflecting surfaces 52 and 54 are arranged to directlight from cathode ray tubes 56 and 58, respectively, toward screen 50.

Reflector 54 has an aperture 55 at the center located on the opticalaxis between a projection system 60 and screen 50. The aperture 55 ispreferably elliptical in shape so that it will appear circular whenviewed along that optical axis. The outer shape of reflector 54 is alsopreferably elliptical, so that it will appear circular when viewed fromthe position of tube 58. However, it is less important that the outeredge of reflector 54 be elliptical than it is that aperture 55 beelliptical, to give a circular boundary around the projector opticalaxis. The shape of aperture 53 within reflector 52 will correspond tothe outer shape of reflector 54.

In operation, light-and-shadow images will be produced on the faces oftubes 56 and 58 by conventional tube control means 62 and 64,respectively. Typical light rays 66 and 68 illustrate the path of lightfrom the tubes, to reflectors 52 and 54, and through lens 70 to screen50. Typically, one tube might present radar images, while the otherprovides alphanumeric data or graphical images. Meanwhile, power supply72 is operated to activate light source 74 to direct light through lenssystem 76 and partially transparent slide 78. This light passes throughaperture 55 and lens 70 to screen 50, as illustrated by typical lightrays 80 and 81. Typically, projection system 60 might provide a map orgrid background on screen 50.

While reflectors 52 and 54 and aperture 55 may have any suitable .sizesand shapes, it is preferred that aperture 55 have a size sufficient topass the significant portion of the zero order diffraction pattern ofslide 78, as discussed above. The sizes of the reflectors and thedistance between the tube faces and the reflectors may be adjusted togive optimum image uniformity and brightness.

While various specific components, arrangements and proportions havebeen described in conjunction with the above description of preferredembodiments, these can be varied or other components used, wheresuitable, with similar results as discussed above.

Further applications and modifications of the present invention willbecome apparent to one skilled in the art upon reading this disclosure.These are intended to come within the scope of this invention, asdefined in the appended claims.

lclaim:

1. An optical system comprising:

a. a first imaging means including a substantially planar diffuse,non-directional, light-and-shadow image source;

b. an apertured reflecting surface positioned at an angle to the planeof said first image source to reflect light emitted thereby saidreflecting surface being substantially totally reflecting;

c. a lens system positioned to receive light reflected by said aperturedreflecting surface and to form an image therefrom on an image plane; and

d. a second imaging means positioned to project light from a directionalimage source through the aperture in said apertured reflecting surface,and through said lens system to form a second image in superimposedregister with said first image on said image plane.

2. The optical system according to claim 1 wherein said first imagingmeans includes a cathode ray tube screen, said second imaging meansincludes a transparency projection system and said image plane includesa sheet of photosensitive material.

3. The optical system according to claim 2 wherein said aperture has asize just sufficient to pass the significant portion of the zero orderdiffraction pattern of the transparency used in said transparencyprojection system.

4. An optical system comprising:

a. first and second spaced imaging means, each including a substantiallyplanar, diffuse, non-directional, light-andshadow image source;

b. a first apertured substantially totally reflecting surface arrangedat an angle to the plane of said first image source to reflect lightemitted thereby along an optical axis;

c. a second apertured substantially totally reflecting surfacepositioned within the aperture in said first reflecting surface,arranged at an angle to the plane of said second image source to reflectlight emitted thereby along said optical axis; I

d. a third imaging means positioned to pro ect light from a directionalimage source through the aperture in said second apertured reflectingsurface along said optical axis; and

e. a lens system positioned along said optical axis receiving light fromeach imaging means to form images in superimposed register in a singleimage plane.

5. The optical system according to claim 4 wherein said first and secondimaging means each includes a cathode ray tube screen, said thirdimaging means includes a transparency projection system and said imageplane includes a sheet of photosensitive material.

6. The optical system according to claim 5 wherein said aperture in saidsecond reflecting surface has a size just sufficient to pass thesignificant portion of the zero order diffraction pattern of thetransparency used in said transparency projection system.

7. An optical system comprising:

a. a cathode ray tube imaging means for forming a difiuse,non-directional, light-and-shadow image on the face thereof;

b. an apertured substantially totally reflecting surface positioned atan angle to said face to reflect light emitted thereby;

c. a lens system positioned to receive light reflected by said aperturedreflecting surface and to form first image on an image planecorresponding to that on said face; and

d. a transparency projection means for projecting a directional image ofa partially transparent original lightand-shadow image through theaperture in said reflecting surface and through said lens system;whereby a second image is formed on said image plane in superimposedregister with said first image.

8. The optical system according to claim 7 wherein said aperture has asize just sufficient to pass the significant portion of the zero orderdiffraction pattern of the transparency used in said transparencyprojection system.

1. An optical system comprising: a. a first imaging means including a substantially planar diffuse, non-directional, light-and-shadow image source; b. an apertured reflecting surface positioned at an angle to the plane of said first image source to reflect light emitted thereby said reflecting surface being substantially totally reflecting; c. a lens system positioned to receive light reflected by said apertured reflecting surface and to form an image therefrom on an image plane; and d. a second imaging means positioned to project light from a directional image source through the aperture in said apertured reflecting surface, and through said lens system to form a second image in superimposed register with said first image on said image plane.
 2. The optical system according to claim 1 wherein said first imaging means includes a caThode ray tube screen, said second imaging means includes a transparency projection system and said image plane includes a sheet of photosensitive material.
 3. The optical system according to claim 2 wherein said aperture has a size just sufficient to pass the significant portion of the zero order diffraction pattern of the transparency used in said transparency projection system.
 4. An optical system comprising: a. first and second spaced imaging means, each including a substantially planar, diffuse, non-directional, light-and-shadow image source; b. a first apertured substantially totally reflecting surface arranged at an angle to the plane of said first image source to reflect light emitted thereby along an optical axis; c. a second apertured substantially totally reflecting surface positioned within the aperture in said first reflecting surface, arranged at an angle to the plane of said second image source to reflect light emitted thereby along said optical axis; d. a third imaging means positioned to project light from a directional image source through the aperture in said second apertured reflecting surface along said optical axis; and e. a lens system positioned along said optical axis receiving light from each imaging means to form images in superimposed register in a single image plane.
 5. The optical system according to claim 4 wherein said first and second imaging means each includes a cathode ray tube screen, said third imaging means includes a transparency projection system and said image plane includes a sheet of photosensitive material.
 6. The optical system according to claim 5 wherein said aperture in said second reflecting surface has a size just sufficient to pass the significant portion of the zero order diffraction pattern of the transparency used in said transparency projection system.
 7. An optical system comprising: a. a cathode ray tube imaging means for forming a diffuse, non-directional, light-and-shadow image on the face thereof; b. an apertured substantially totally reflecting surface positioned at an angle to said face to reflect light emitted thereby; c. a lens system positioned to receive light reflected by said apertured reflecting surface and to form first image on an image plane corresponding to that on said face; and d. a transparency projection means for projecting a directional image of a partially transparent original light-and-shadow image through the aperture in said reflecting surface and through said lens system; whereby a second image is formed on said image plane in superimposed register with said first image.
 8. The optical system according to claim 7 wherein said aperture has a size just sufficient to pass the significant portion of the zero order diffraction pattern of the transparency used in said transparency projection system. 